1. Field of the Invention
The present invention relates to an image reading apparatus and a method of displaying an alien substance location thereof, and in particular to assistance provided to a user to realize elimination of an alien substance on a light path between a document and a reading device in a document-feed-type image reading system, which is a factor of a line-like image, by clearly showing the location of the alien substance in an actual machine.
2. Description of the Related Art
Conventionally, an image reading apparatus equipped with an auto document feeder (ADF) is known. The image reading apparatus is provided with a “feeding-document reading mode” for reading documents with moving the documents at a constant speed one by one by the auto document feeder, while an optical scanning unit for emitting light to the document and scanning light reflected from the document is stopped at a predetermined document reading location. In this “feeding-document reading mode”, since the documents only have to be simply moved in a constant direction, there is a merit that the time elapsed from a document reading to another document reading is shorter in comparison with a scanning operation of the optical scanning unit in the case of continuously reading a great number of documents.
However, in this “feeding-document reading mode”, there is a problem that, if dust or dirt adheres to the document reading location of an original plate, a black line-like image occurs on a read image in a sub-scanning direction at a location corresponding to the location of the dust or dirt. Accordingly, as a method of solving the problem of the occurrence of a black line-like image, the methods as shown below have been proposed.